My fire stick worked for about 3 months then it started shutting down and restarting every 3 or 4 minutes. I figured out that it was overheating if I let it cool completely (stuck it in the freezer) it would run for about a half an hour then do the reset thing again. I opened it up and the circuit board has a large flat piece of metal that is supposed to be a heat sink it obviously isn’t large enough. I purchased on Amazon the following heat sink parts https://www.amazon.com/gp/product/B07217...

I stuck as many as would fit on the heat sink in the fire stick (you have to leave the case off) and watched 4 hours of movies without interruption. I unplug the power cord when I’m not using it so it doesn’t have a chance to overheat when I don’t need it.